Evaluation of botanical herbicides against common weed species of coffee (Coffea arabica L.) with emphasis on bidens pilosa at southwestern Ethiopia
Despite the wealth of genetic diversity of Arabica coffee, the national average yield of Ethiopian coffee is very low compared with many other producer countries. Weeds are one of the most limiting constraints particularly in organic farming systems, as no synthetic herbicides are allowed due to their direct and indirect negative impacts on the production system and the health care as well. There are tremendous strives to use cultural practices or to search for alternative weed control methods globally. The current study was conducted to test the inhibitory potential of essential oils extracted from eight locally available plants and three inert minerals against common weed species of coffee with emphasis on Bidens pilosa both under lath house and field conditions with application frequency of once, twice and three times at the rate of 5% (v/v) in RCBD with three replications. For the purpose of comparison, negative and positive controls were included in both experiments. The result showed that few plant extracts reduced the growth and total biomass of B. pilosa seedlings over the control in pot culture under lathhouse condition. The inhibitory effects of botanical herbicides were varied among plant extracts as well as with application frequency. Essential oils extracted from E. citrodora and C. winterianus caused significantly the highest percentage growth retardation of weeds as compared to untreated control. Inhibitory effects of tested materials were application frequency dependant, at lower application frequency (1x), comparatively less reduction in all growth parameters were recorded than application at higher frequency (3x). Therefore, it can be concluded that essential oils from E. citrodora and C. winterianus using three times application frequency have the potential to retard growth weed species in coffee farm. The future research should give emphasis to develop IPM of coffee weeds with integrating biocontrol approaches such as bioherbicides as the proven finding of this investigation.